Semiconductor device with groove structure to prevent molding resin overflow over a light receiving region of a photodiode during manufacture

ABSTRACT

A semiconductor device having a substrate including a photodiode; a resin layer formed on an upper surface of the substrate, the resin layer not covering a light receiving region of the photodiode, the resin layer including at least one groove surrounding the light receiving region; and a molding resin portion formed by mold-sealing the photodiode with the resin layer thereon so as not to cover the light receiving region.

RELATED APPLICATION DATA

This application is a division of U.S. patent application Ser. No.12/398,520, filed Mar. 5, 2009, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentapplication claims the benefit of priority to Japanese PatentApplication No. JP 2008-084568 filed in the Japanese Patent Office onMar. 27, 2008, the entirety of which is incorporated by reference hereinto the extent permitted by law.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a method formanufacturing the semiconductor device. In particular, the presentinvention relates to a semiconductor device that includes a photodiodeand is mold-sealed with a molding resin such that the molding resin doesnot cover the light receiving region of the photodiode; and a method formanufacturing the semiconductor device.

Optical disc players are widely used for playing data recorded onoptical discs such as CD-R (compact disc recordable) and DVD-R (digitalversatile disk recordable).

Such an optical disc player includes an irradiation unit for irradiatinga data recording surface of an optical disc with laser light(hereinafter, referred to as “light”) for reading data; an opticalpickup for receiving reflected light from the data recording surfacethat reflects the light from the irradiation unit and outputting datasignals in accordance with the intensity of the received light; and asignal processing circuit for subjecting the data signals from theoptical pickup to predetermined signal processing to produce signalsthat can be displayed with displays and the like.

The optical pickup has, in its light receiving portion, a photo detectorintegrated circuit (PDIC) including a photodiode. The photodiodefunctions as a photoelectric conversion element for converting receivedlight into electric signals.

For the purpose of protecting semiconductor elements in such a PDIC froman externally applied impact, dust, moisture in the ambient atmosphere,and the like, the PDIC is packaged by sealing the PDIC with an epoxyresin or the like such that the light receiving region of a photodiodeis not covered by the epoxy resin or the like (For example, see JapaneseUnexamined Patent Application Publication No. 2003-017715).

A semiconductor device such as the packaged PDIC above is typicallymanufactured by bonding a substrate including semiconductor elementssuch as a photodiode onto a lead frame serving as a base; thenconducting wire bonding by bonding the terminals of a PDIC to theterminals on the lead frame with metal wires; and subsequently loadingthe lead frame including the PDIC into a mold with a predetermined shapeand filling the mold with a sealing resin liquefied by heating.

SUMMARY OF THE INVENTION

In manufacturing of semiconductor devices including photodiodes by theabove-described method, when a mold is filled with a sealing resin, theresin can flow into the light receiving region of a photodiode. This iscaused, for example, by variations in the shapes of the photodiodes.

Such a flowing of a sealing resin into the light receiving region of aphotodiode can reduce the size of the light receiving region, therebydecreasing the sensitivity of the photodiode to light.

In the above-described method, a heated sealing resin is brought intodirect contact with semiconductor elements such as a photodiode. Theheat applied to the semiconductor elements in this step can alter theshape or the characteristics of the semiconductor elements in regionsother than the light receiving region of the photodiode. This candegrade the characteristics of the semiconductor elements, therebyreducing device yield.

A method for manufacturing a semiconductor device according to anembodiment of the present invention includes the steps of: forming aresin layer on an upper surface of a substrate including a photodiode;forming, in the resin layer, an opening through which a surface of alight receiving region of the photodiode is exposed; forming at leastone groove in the resin layer so as to surround the light receivingregion; and subsequently mold-sealing the photodiode by loading thesubstrate into a mold and filling the mold with a molding resin.

In this method, the at least one groove may include a plurality ofconcentric circular grooves having different diameters.

In the above cases, the light receiving region and the at least onegroove may be covered with a resin film before the mold is filled withthe molding resin.

In the above cases, in the step of forming the at least one groove, theresin layer may be allowed to remain on the upper surface of thesubstrate in a region surrounding the at least one groove.

In the above cases, the resin layer may be formed with a polyimideresin.

A semiconductor device according to another embodiment of the presentinvention includes a substrate including a photodiode; a resin layerformed on an upper surface of the substrate, the resin layer notcovering a light receiving region of the photodiode, the resin layerincluding at least one groove surrounding the light receiving region;and a molding resin portion formed by mold-sealing the photodiode withthe resin layer thereon so as not to cover the light receiving region.

A semiconductor device according to still another embodiment of thepresent invention includes a substrate including a plurality ofsemiconductor elements including a photodiode; a resin layer formed onan upper surface of the substrate, the resin layer not covering a lightreceiving region of the photodiode, the resin layer including at leastone groove surrounding the light receiving region; and a molding resinportion formed by mold-sealing the semiconductor elements with the resinlayer thereon so as not to cover the light receiving region.

The present invention can provide a semiconductor device that includes aphotodiode with high sensitivity to light and a method for manufacturingthe semiconductor device in a high yield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C, and 1D are explanatory views showing steps inmanufacturing a semiconductor device according to an embodiment of thepresent invention;

FIGS. 2A, 2B, 2C, and 2D are explanatory views showing steps inmanufacturing a semiconductor device according to an embodiment of thepresent invention;

FIGS. 3A and 3B are explanatory views showing steps in manufacturing asemiconductor device according to an embodiment of the presentinvention;

FIG. 4 is an explanatory view showing a step in manufacturing asemiconductor device according to an embodiment of the presentinvention; and

FIGS. 5A, 5B, and 5C are explanatory views showing steps inmanufacturing a semiconductor device according to an embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a method for manufacturing a semiconductor device accordingto an embodiment of the present invention and a semiconductor devicemanufactured by the method will be specifically described with referenceto FIGS. 1A to 5C.

The embodiment described below is an example in which the presentinvention is applied to a manufacturing step where a photo detectorintegrated circuit (PDIC) having semiconductor elements including aphotodiode on a single semiconductor substrate is packaged with asealing resin. The present invention is not restricted to theembodiment. The present invention is applicable to any packaging step inwhich a semiconductor element is sealed with a resin or the like suchthat the semiconductor element is not entirely covered with the resin orthe like. Such a packaging step may include a packaging step in which asingle semiconductor element having a light receiving region is sealedwith a resin or the like such that the light receiving region is notcovered with the resin or the like.

Note that the embodiment is described in terms of a packaging step inwhich a PDIC is sealed with a resin. For other steps for forming thePDIC performed prior to the packaging step, existing manufacturing stepsmay be used. Thus, such steps are not described below.

FIGS. 1A, 1C, 2A, 2C, 3A, 3B, 4, 5A, and 5B are explanatory viewsshowing cross sections of configurations in steps for manufacturing asemiconductor device according to the embodiment. FIG. 1B is anexplanatory view, in plan, of the configuration in FIG. 1A. FIG. 1D isan explanatory view, in plan, of the configuration in FIG. 1C. FIG. 2Bis an explanatory view, in plan, of the configuration in FIG. 2A. FIG.2D is an explanatory view, in plan, of the configuration in FIG. 2C.FIG. 5C is an explanatory view, in perspective, of a semiconductordevice manufactured by the method according to the embodiment.

Manufacturing of a semiconductor device (hereinafter, referred to as“PDIC”) in FIG. 5C is described below. As shown in FIGS. 1A and 1B, astructure (hereinafter, referred to as “chip 1”) is prepared thatincludes, on a single semiconductor substrate 3, a photodiode 2 formedby existing manufacturing steps and other semiconductor elements (notshown) such as transistors, metal insulator semiconductor (MIS)capacitive elements, and polysilicon resistors. Electrode pads 6 inFIGS. 1A and 1B function as the anode electrode and the cathodeelectrode of the photodiode 2.

As shown in FIG. 1A, the chip 1 has a light receiving region 5 of thephotodiode 2 in a substantially central portion of the front surface ofthe chip 1. As shown in FIG. 1B, the light receiving region 5 iscircular in plan view.

A multilevel interconnection layer 4 including wires interconnectingsemiconductor elements on the chip 1 in accordance with the design ofthe chip 1 is formed around the light receiving region 5.

As shown in FIGS. 1C and 1D, a resin layer 7 is then formed with apolyimide resin on the entirety of the upper surface of thesemiconductor substrate 3 including the photodiode 2.

Specifically, the resin layer 7 is formed as follows. A pretreatmentagent is spin-coated over the entirety of the upper surface of the chip1 by adding dropwise the pretreatment agent onto the light receivingregion 5 of the photodiode 2 while the chip 1 is being rotated at acertain rate.

Likewise, a polyimide resin is then spin-coated over the thus-formedpretreatment agent layer of the chip 1 by adding dropwise the polyimideresin onto the chip 1 while the chip 1 is being rotated at a certainrate. Thus, the resin layer 7 is formed so as to have a thickness of 5to 15 μm.

In the present embodiment, the resin layer 7 is formed with a polyimideresin that blocks light when being cured.

A resist mask (not shown) is then formed on the resin layer 7 byapplying a photoresist onto the resin layer 7 and patterning thethus-formed photoresist layer by photolithography techniques.

After that, the resin layer 7 is wet-etched through the resist mask, sothat portions of the resin layer 7 that are not covered with the resistmask are selectively removed. As a result, as shown in FIGS. 2A and 2B,there are formed an opening through which the surface of the lightreceiving region 5 is exposed and grooves 8 in the resin layer 7. Thegrooves 8 are formed so as to surround the light receiving region 5.

Alternatively, the opening, the grooves 8, and the like may be formedwithout a resist mask by adding a sensitizer to a polyimide resin toprepare an optically sensitive polyimide resin, forming the resin layer7 with the optically sensitive polyimide resin, and subjecting the resinlayer 7 to a certain pattern exposure treatment.

As shown in FIG. 2B, the grooves 8 are formed as five closed-loopgrooves that surround the light receiving region 5. Although the numberof the grooves 8 is five in the present embodiment, the presentinvention is not restricted thereto. At least one groove is formed asthe groove 8 and preferably five or more grooves are formed as thegrooves 8.

The grooves 8 are formed to have a width of about 20 μm and at a pitchof about 20 μm.

As fully described below, the grooves 8 function as dams for preventinga sealing resin from flowing into the light receiving region 5 of thephotodiode 2 when the PDIC is mold-sealed with the sealing resin.

As shown in FIG. 2B, the grooves 8 are formed so as to be concentriccircular grooves, in plan view, having different diameters with thecenter of the grooves being at the center of the light receiving region5 of the photodiode 2.

Since the grooves 8 are circular in plan view, the grooves 8 can preventa resin from flowing into the light receiving region 5 from anydirection in a mold-sealing step performed later.

Although the grooves 8 are circular in plan view in the presentembodiment, any shape will suffice as long as the grooves 8 areclosed-loops in plan view such as rectangles or polygons.

When the grooves 8 are formed to be polygons in plan view, the resistmask can be formed to have a less complex pattern on the resin layer 7.

When the grooves 8 are formed, the resin layer 7 is removed in a portionon the light receiving region 5 of the photodiode 2, portions where thegrooves 8 are formed, and portions on the electrode pads 6 on the chip1. The resin layer 7 is not removed other than these portions and lefton the multilevel interconnection layer 4.

That is, in the present embodiment, the semiconductor elements otherthan the photodiode 2 are covered by the resin layer 7.

As described above, the resin layer 7 blocks light. In the configurationwhere the resin layer 7 covers the semiconductor elements other than thephotodiode 2, the resin layer 7 prevents unwanted light through regionsother than the light receiving region 5 from entering the lightreceiving region 5. As a result, the photodiode 2 can exhibit anenhanced sensitivity to light.

The chip 1 is then subjected to a curing treatment for about 2 hours ata temperature of about 350° C., so that the resin layer 7 is cured. As aresult, properties of the resin layer 7 such as mechanical strength,heat resistance, and chemical resistance are enhanced.

The chip 1 is then subjected to an ashing treatment for removingresidues generated in the formation of the resin layer 7. After that,the back surface of the chip 1 is polished by chemical mechanicalpolishing (CMP) so that the thickness of the semiconductor substrate 3is adjusted (not shown).

As shown in FIGS. 2C and 2D, die bonding is conducted by fixing the chip1, which includes the grooves 8 in the resin layer 7, on a lead frame 10through an adhesive layer 11. After that, wire bonding is conducted bybonding the electrode pads 6 on the chip 1 to electrode pads 12 on thelead frame 10 with metal wires 13.

As shown in FIG. 3A, a resin film 22 with a certain elasticity isattached to the inner surface of a mold 21 for mold-sealing the chip 1.A platform 20 in FIG. 3A is used for placing the chip 1 thereon when thechip 1 is mold-sealed.

As shown in FIG. 3B, the chip 1, which is fixed to the lead frame 10, isplaced on the platform 20; and the mold 21 is then lowered such that aprojected portion in the center of the inner surface of the mold 21 ispressed against, through the resin film 22, the light receiving region 5of the photodiode 2 and the portion including the grooves 8 surroundingthe light receiving region 5.

In this way, the light receiving region 5 and the grooves 8 are coveredby the resin film 22 prior to filling of the mold 21 with a moldingresin 23.

In this case, the projected portion in the center of the inner surfaceof the mold 21 is pressed against the upper surface of the chip 1. Inthe present embodiment, the resin film 22 with a certain elasticity,which is attached to the inner surface of the mold 21 in advance,functions as a buffer and prevents the projected portion from cominginto direct contact with and damaging the light receiving region 5.

After that, as shown in FIG. 3B, the periphery of the chip 1 ismold-sealed such that the light receiving region 5 is not covered by themolding resin 23. Specifically, the space defined by the inner surfaceof the mold 21 and the periphery of the chip 1 is filled with themolding resin 23 (e.g. an epoxy resin) liquefied by heating. The moldingresin 23 is introduced into the space through an inlet disposed at alower periphery of the chip 1.

FIG. 4 is an enlarged explanatory view showing a portion including thelight receiving region 5 and the grooves 8 in this mold-sealing step.

As shown in FIG. 4, when the mold 21 is filled with the molding resin 23in the mold-sealing step, the molding resin 23 is subjected to apressure and a portion of the molding resin 23 can flow for the lightreceiving region 5 through the gap between the resin layer 7 and theresin film 22.

When the molding resin 23 reaches the light receiving region 5, the areaof the light receiving region 5 is decreased and as a result thephotodiode 2 can have a degraded sensitivity to light. However, asdescribed above, in the method for manufacturing a semiconductor deviceaccording to the present embodiment, the plurality of grooves 8 areformed in the resin layer 7 so as to surround the light receiving region5, the resin layer 7 being formed on the multilevel interconnectionlayer 4 of the chip 1. This configuration satisfactorily prevents themolding resin 23 flowing for the light receiving region 5 from reachingthe light receiving region 5.

Specifically, when pressure is applied to the molding resin 23 so thatthe mold 21 is filled with the molding resin 23, the molding resin 23flows into the region where the grooves 8 are formed from thecircumference of this region toward the inner portion of the region. Atthis time, the grooves 8 function as dams for receiving the moldingresin 23 flowing for the light receiving region 5 and the resin layer 7inbetween the grooves 8 functions as walls for blocking the moldingresin 23 flowing for the light receiving region 5. In this way, themolding resin 23 is satisfactorily prevented from reaching the lightreceiving region 5.

In filling of the mold 21 with the molding resin 23, the resin film 22with a certain elasticity is disposed between the grooves 8 and theprojected portion in the center of the inner surface of the mold 21. Theelasticity of the resin film 22 can absorb a portion of the pressureapplied to the molding resin 23. This also suppresses flowing of themolding resin 23 into the light receiving region 5.

When the mold 21 is filled with the molding resin 23, which is liquefiedby heating, the heat of the molding resin 23 is transferred to the chip1. However, in the present embodiment, the resin layer 7 formed with apolyimide resin having a good heat resistance covers the multilevelinterconnection layer 4 of the chip 1 except the light receiving region5 of the photodiode 2, the region where the grooves 8 are formed, andthe region where the electrode pads 6 are formed. The resin layer 7protects the multilevel interconnection layer 4 and the semiconductorelements under the layer 4 from the heat of the molding resin 23. As aresult, the product yield can be increased.

Since the resin layer 7 formed with a polyimide resin has a coefficientof expansion as low as those of metals, contact with the heated moldingresin 23 causes negligible expansion or deformation of the resin layer7.

As a result, filling the mold 21 with the molding resin 23 at a hightemperature does not result in problems such as disconnection of wiresin the underlying multilevel interconnection layer 4 caused by thermalexpansion and deformation of the resin layer 7. Thus, a decrease in theproduct yield can be prevented.

As shown in FIG. 5A, the mold-sealed chip 1 is then detached from themold 21 and diced into PDICs.

Finally, as shown in FIG. 5B, to prevent dust or the like from adheringto the light receiving region 5 of the photodiode 2 duringtransportation or mounting of the PDICs, a protective film 25 isattached to the upper surface of each PDIC. Thus, the PDIC shown in FIG.5C is obtained.

In summary, in the present embodiment, PDICs are manufactured by amethod for manufacturing a semiconductor device, including the steps of:forming a resin layer on an upper surface of a substrate including aphotodiode; forming, in the resin layer, an opening through which asurface of a light receiving region of the photodiode is exposed;forming at least one groove in the resin layer so as to surround thelight receiving region; and subsequently mold-sealing the photodiode byloading the substrate into a mold and filling the mold with a moldingresin. In the mold-sealing step, the molding resin with which the moldis filled can be prevented from flowing into the light receiving regionof the photodiode.

As a result, a decrease in light sensitivity of a PDIC caused by flowingof the molding resin into the light receiving region can be prevented.Thus, the product yield can be increased.

In the present embodiment, a plurality of concentric circular grooveshaving different diameters are formed. In this configuration, even if anouter groove does not hold back the molding resin, inner grooves canhold back the molding resin.

In the present embodiment, since the light receiving region and thegrooves are covered by the resin film prior to filling the mold with themolding resin, the resin film prevents the mold from coming into directcontact with and damaging the PDIC in the mold-sealing step.

In the present embodiment, in the step of forming the grooves, the resinlayer is allowed to remain on the upper surface of the substrate in aregion surrounding the grooves. In this configuration, the resin layerprotects the PDIC from the heat of the heated molding resin.

As a result, degradation of the characteristics of the PDIC caused bythe heat of the molding resin can be prevented. Thus, the product yieldcan be increased.

In the present embodiment, the resin layer is formed with a polyimideresin having an extremely low thermal expansion coefficient. Thepolyimide resin, after being cured, also exhibits high mechanicalstrength, high heat resistance, high chemical resistance, and thecapability of blocking light. As a result, the resin layer can protectthe PDIC from various stresses applied during the manufacturing steps,and hence, the product yield can be further increased.

Use of the method for manufacturing a semiconductor device according tothe present embodiment can provide a PDIC including a substrateincluding a plurality of semiconductor elements including a photodiode;a resin layer formed on an upper surface of the substrate, the resinlayer not covering a light receiving region of the photodiode, the resinlayer including at least one groove surrounding the light receivingregion; and a molding resin portion formed by mold-sealing thesemiconductor elements with the resin layer thereon so as not to coverthe light receiving region.

In the method, the molding resin used in the mold-sealing does notadhere to the light receiving region of the photodiode, and hence, thearea of the light receiving region is not decreased. Thus, the resultingPDIC can have a high sensitivity to light. Furthermore, there is lessvariation in sensitivity to light among the PDICs, and hence, theproduct yield can be enhanced.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A semiconductor device comprising: a substrateincluding (a) a photodiode having a light receiving region, (b) aninterconnection wiring layer around the light receiving region, and (c)electrode pads on an upper surface of the interconnection wiring layer;an organic layer on an upper surface of the interconnection wiringlayer, the organic layer not covering the light receiving region of thephotodiode and not covering the electrode pads, the organic layerincluding (i) a groove continuously surrounding the light receivingregion and (ii) portions that expose the electrode pads, the organiclayer being disposed around the electrode pads; and a molding resinportion over the substrate with the organic layer thereon so that themolding resin portion does not cover the light receiving region.
 2. Thesemiconductor device of claim 1, further comprising a protective film incontact with the molding resin portion, the protective film covering thelight receiving region.
 3. The semiconductor device of claim 1, whereinthe organic layer comprises a polyimide resin.
 4. The semiconductordevice of claim 1, further comprising: a plurality of groovescontinuously surrounding the light receiving region.
 5. Thesemiconductor device of claim 4, wherein the plurality of grooves areclosed-loop grooves.
 6. The semiconductor device of claim 1, wherein thegroove is between the light receiving region and the electrode pads. 7.A semiconductor device comprising a substrate including a plurality ofsemiconductor elements, at least one of which includes: (a) a photodiodehaving a light receiving region, (b) an interconnection wiring layeraround the light receiving region, and (c) electrode pads on an uppersurface of the interconnection wiring layer; an organic layer on theupper surface of the interconnection wiring layer, the organic layer notcovering the light receiving region of the photodiode and not coveringthe electrode pads, the organic layer including (i) a groovecontinuously surrounding the light receiving region and (ii) portionsthat expose the electrode pads, the organic layer being disposed aroundthe electrode pads; and a molding resin portion over the substrate withthe organic layer thereon so that the molding resin portion does notcover the light receiving region.
 8. The semiconductor device of claim7, wherein the interconnection wiring layer is a multilevelinterconnection wiring layer that includes wires interconnecting theplurality of semiconductor elements on the substrate.